Method and means for the recordation of sound



Feb. 11, 1936- .c. L. OSWALD El AL 2,030,750

METHOD AND MEANS FOR THE RECORDATION OF SOUND I Original Filed Oct. 29, 1923 3 Sheets-Sheet 1 w @J Q Q w f mm m 4 1 L a um .m 16 w 0 0 4 l C. 5 5 m. mm 5 M P J lk m T m. My :5 IEJM lq 4U t f 2 U 64/? Q F 61bsmn um 96 6 a ZN x .J:\\ m v GNU M \H\\\\\H\ W 7/////// 4 5 m nw N, A 1

Feb. 11, 1936. 2,030,760

METHOD AND MEANS FOR THE RECORDATION OF SOUND C. L. OSWALD ET AL 3Sheets-Sheet 2 Original Filed Oct. 29, 1923 ATTRNEY Feb. 11, 1936. Q QSWALD AL 2,030,760

METHOD AND MEANS FOR THE RECORDATION OF SOUND Original Filfid 001;. 29, 1923 3 Sheets-Sheet 3 are J6 J I -56 f6 6 -5 J2! 1 123214 Ans wwauk QM AT'ToRNEYs.

Patented Feb. 11, 1936 PATENT METHOD AND MEANS FOR THE BECORDA- v H, y

' TION OF SOUND Carl Louis Oswald, New York, N.- Y., and Warren Dunham Foster, Washington Township, Bergen County, N. 1., assignors, by direct and'mesne 1 I assignments, to Kinatome Patents Corporation, a corporation of New York Original application October 29, 1928, Serial No.

315,761; now Patent No. 1,928,392, dated September 26, 1933. 'Divided. and this application August 21, 1933, Serial No. 686,154. In Great Britain October 26, 1929 zi'ciaims. (c|. ire-100.3)

The present invention relates broadly to the art of recording sound upon light sensitive material by photo electrical means, but it will be.

improved method and means whereby sound may be recorded more accurately than heretofore has been possible,-either independently or in conjunction-with pictures.

A related object is the photographing upon film from which sound is to be reproduced, of lines or masses which are so clear and distinct, and of such uniform density, that sound waves reproduced from them will be clear, distinct and true.

In the past, attempts to secure such clear and uniform photographic images have led to the adoption of various expedients which in, turn have led to difllculties. One common plan has been the use of a slot so narrow that only with difliculty can it,- be constructed with sufficient 0 accuracy for practical efiiciency. In many cases, the film has been fed in closephysical contact with the medium containing the slot, thus rapidly filling the slot with dirt, dust, and portions of emulsion or cellulose from the film, and also put- 5 ting an undue strain upon the film. While we provide a satisfactory means for the construction 01' a slot of extremely small width and for'keeplng it free trom obstructions as is claimed incur parent patent, in apparatus constructed accord- 3 ing to certain of the preferred forms of our invention it is not necessary to provide a slot of such extreme narrowness or to run the film in actual contact with the material forming or covering the slot.

3 Under current practice, it has been thought necessary to restrict the area of the efiecti've image formed by the sound which is being recorded to the exact area of the slot through which the actuating light passes, thus creating obvious restrictions. In apparatus constructed according to a preferred form of our invention, the area of the elective image may be materially smaller thanthat of the slot, and in that made according to another preferred form'it may be slightly larger.

Our invention is applicable for Another object of our invention is to na e possible the use of photographic images in lines or mass formations,representing sounds which it is desired to record for reproduction, which photographic images may be materially smaller 5 than such as now are common in the art. We are A able by such means to make useof many more sound images or'tone symbols in a givenlength of film, greatly increasing its tonal time equiva:

lent and range and consequently also greatly. o augmenting the effectiveness, in a given time J period of combined sound and picture reproduction. Moreover, our invention has particular usefulness in connection with motion picture and phonograph apparatus which employs films of 16 millimeters or 9 millimeters in width or of some other size primarily designed for home use and which are of'less than the so called theatrical standard of 35 millimeters width. Obviously upon such films, which, because of economy and 20 other commercial conditions, are now well established for domestic use, the area which isavailw able for the sound image is very much reduced; As a consequence the difficulties which have arisen from ill defined photographic images, representing sound impulses, when these are im- I printed upon millimeter film, have been greatly exaggerated when such images have been correspondlngly reducedin size for use -upon 16 millimeter or other so called sub-standard films. Our .30 invention makes it possible to secureupon 16 millimeter film, for example, as clear and accuj rate sound images as those which previously'have been secured upon 35 millimeter film, and can be.

applied with corresponding effect to fllms of even 35 smaller dimensions. v

. Under present practice, inaccurate and consequently unpleasant sound reproductions have re-. suited from undesired fluctuations in the theoretically constant light source of the recording 40 apparatus. Our invention includes means for obviating such difficulties. l

Another object of our invention is to add to the electrical and acoustic means' commonly em- .ployed in the recordation of sound. images certain to photographic methods, meansand technique in such" manner as" to secure improvement .in the quality of sound translation andsubsequentre translation. By the employment of the appa-. ratus and the means and methods herein described, it is possible to assure the integrity 0'! the latent soundimage as of the moment at which it is implanted upon theph'oto-sensitive material. --A further object of our invention is the treatment of. that latent iinage by such 2 a chemical choserfwith due res'ardtothemeansandmethodswhichhadbeen emplpyed'to-implant the latent image and the of -the particular photo-sensitive material employed, as will retain in the stable and completed sound image the quality imparted by such previous steps in the process.

Another object of our invention is to provide 1 for the taking of talking pictures or of films for film playing phonographs, which may stood that we are not limited to these particular constructions and processes as changes can be readily made without departing from the spirit of the invention or the scope of our broader It will be readily understood by those skilled in the art'that our invention applies to sound apparatus generically. Itwillalso be readily understood that our invention may be ap'plied'to any art in which the accurate and controlled recordation of a photographic image isuseful or necessary in the exercise of control or translation by means of light.

In the drawings: a

Figure 1 is a =1 tic representation of" dim-action occurring as light passes through an aperture, greatlyexaggerated for the purpose of Figure Its a diagrammatic section along the suriaceII-IliofthefilmlofFigurei.

Figure 3 is a diagrammatic'view of one form of our invention as embodied in a sound recording instrument.

Figure 4 is a tie view of one form of our invention as embodiedin a sound recording Y instrument ofa type difierent from that represented by Figure 3.

' Figure 5 illustrates, in a form greatly exaggerated for clarity, the effects of refraction and difiraction in connection with a slot and a glass or other cover therefor.

Figure 6 is a diagrammatic representation of .the application of one form of our invention, in-' cluding an optical element, to a'recording apparatus.

Figure 7 shows one means for cleaningthe slot. Figure 8isasection ontheline VIII-VIIIof tic representation of me form of ouroiconverging lightin are-.

Figure 10 shows'one form of film gate as employedjry us and Figure 11 is a tie representation of a substitute therefor.

Figures 12, 13, and 14 show details of a slot structure which we may employ.

Figure 15 shows means employed by us to maintain a light source at a constant temperature and-point of incandescence. I

'Throughout the drawings and specifications, like characters apply to like parts. For the purpose oi greater simplicity, like parts which are duplicated in various embodiments 0! our invention receive the same reference numerals except where clarity demands otherwise.

In carrying out our invention,'we employ light of a predetermined wave length. We select light 0! that particular rate of vibration which has the photographic qualities which are desirable fo the particular result which is to be obtained. For example, when we select light from the visible spectrum, we employ-monochromatic light of a selected color or wave length, for the re-' cordation oi the photographic image representing the sound waves.

From amongthe many photographic emulsions which are available, we are not compelled to choose in accordance with the limiting requirements of white light but are enabled to use in each employment of our invention the photographic emulsion which is best suited to the re-, quirements of the particular conditions then applying and to employ in each instance that particular form of lightwhich will be best suited image as well as of that portion of the film bearing the sound image, in case both' images are implanted upon the same strip. Thus it *will be seen that we choose that particular combination of light, emulsion, and developer which will result'in the most satisfactory sound and pictorial images under the given conditions. In present common practice, poiychromatic light, ordinarily spoken of as white light, is employ in apparatus using visible light for the electrical recordation 0! sound. Even with the use of a better photographic technique. than is now common, polychromatic light would still cause many of the difiiculties to which reference has already been had and will later be made.

For purposes entirely difierentfrom those embraced within or'pertinent .to our-invention, it has been proposed to employ visible colored images for use as sound records. ,We do not use colored images as part of or in carrying out our invention of sound recordation. We use what is ordinarily known as colored light, but the latent acteristics, requirements or purposes of colored images or photography. It will therefore be understood by those skilled in the art, that our in vention does not require the use of the special and expensive films and apparatus, which have beenproposed to'be used for purposes different from our own, .nor,are we limited by the many photographic and practical difilculties associated with the use of so called colored films.

When reference in this specification or in the claims which a part hereof is made to black and whi films, it is understood that such terminology is used with the meaning common in the motion picture art. Such black and white films may be colored by tinting or toning or any other similar process, whether carried on as supplementary to the regular development and fixing or otherwise. Moreover, the term. may be which is colored or tinted, provided the emulsion used thereon is one of those ordinarily associated' with the making of black andwhite images if used with an ordinary white or gray base. It

images produced thereby, when rendered stable and visible by development, are what are known as black and white. They have none of the charused to include films which are made upon a base will be understood, of course, that when it is desired to use color for the pictorial portion of the film, our process may be applied to that portion 'of the negative which is reserved for the symbols representing sound.

It will be noted in the subjoined claims that the step of moving the film, ormeans for moving the film, is not specifically included, although, as well known to those skilled in the art, and as is stated herein, sound is ordinarily recorded upon a moving film. Such omission in the claims of an obvious step or means is to avoid encumbering the claims with unnecessary words, since, wherever necessary, the inclusion of this obvious step or means will be understood.

In this specification, we often make use of the older term slot as designating the aperture which restricts the light reaching the film, but it will be understood that that term is to be taken as synonymous with the word slit, as used elsewhere in the specification and in the claims. The processes of the electrical recordation of sound upon a photographic film or similar light sensitive surface are of course well understood. The film or other light-sensitive material is moved continuously at a uniform speed and upon it, generally through a slot; 2. light is projected, varying in accordance with the amplitude of the sound waves which are being recorded. Thus there is imprinted upon the light sensitive surface a series of images the photographic density of which varies'in accordance with the variations of the sounds which are being recorded. The resulting images may appear to the eye to be a series of lines of varying intensity. These lines in the negative indicate by means of greater density the nodes oi the sound waves and by less density the anodes of the sound waves, or, in case of theuse of photo-electric cells, of a certain less usual type to control the fluctation of the light, the reverse is true.

As a matter of convenience, it is to the above indicated method of sound recordation that reference will most often be made; It will be readily understood, however, that our invention is equally applicable to any form of sound recordation which depends upon the implantation of photographic images'upon a light sensitive'material, whether, for example, such images take the forms commonly known as variable density or variable area or any other form.

Figure 1 illustrates in a much exaggerated form the edge diffraction which is caused by passing polychromatic light through a narrow slot of the type commonly used in the art. The degree of diffraction which results from passing white light over an. edge is directly proportioned to the lengths of the several waves which make up the light. Thus the rays of the longer wave lengths are difl'racted to a greater extent than are those which are of'lesser amplitude. In Figure 1, I

represents a beam of polychromatic light of.

which 2 is the axis.

In this and many of the following drawings,

for convenience we show the light as a straight line such as I. It will be understood that, except asdefinitely stated, we do not limit ourselves to an optical system of system, in the form of parallel, divergent or convergent light. If desired, a mirror or other reflecting element, not shown, I behind the light source. This light in passing through the opening 3 in the aperture plate 4 is diifracted in accordance with the wave lengths of its component Thus the infra-red rays 8 and 8' show the maximum diffraction, the visible red rays 1 and l" the next degree of difany particular nature. The light may be projected, by any suitable optical may be employed diffraction of the sub-primary colors not being shown. I

As, these rays of varying wave lengths fall upon the-film 5, as is well illustrated in Figure 2 of the drawings, thereare transverse bandsmf the light sensitive emulsion which are subjected to rays of different colors. Every light sensitive emulsion has varying degrees of sensitivity to diiferent colors. As a result of such varying sensitivity, while the entire portion of the emulsion between the lines .II and II is acted upon with approximate uniformity by the white light, the bands from l0 and ID to 6 and 6, both inclusive, are acted upon in degrees varyingaccording to the sensitivity to color of the particular photographic emulsion which is being used at the time. As a result the portions of the entire line or mass which lie between H and I5 and H' and 6' respectively are lacking in uniform photographic density, the portion between' H and II being more nearly uniform.- In other words, the edge is not clear and straight. ragged and muddy. As a result, when a reproduction of the photographic image which is bounded by such an edge is used to actuate a photo-electric cell in the reproduction of. sound, what the auditor hears is likewise unclear, "muddy and blurred. It will be readily recognized that any blurringof a recorded photographic image caused by such diffraction will result in a corresponding blurring of the sound which is reproduced therefrom.

We have found that much of the diiliculty in the past blamed generally upon diffusion", and even photographic grain". is in reality due to the lack of a correct photographic definition caused 44 by fringing colors, which in turn are the of diffraction as stated above.

It will be readily understood that the more narrowly the slot is restricted in size, the more result pronounced will'be such imperfections.

' In Figure 3 we show diagrammatically one embodiment of our invention applicable to a sound recording system such, for example, as one which employs an immovable light supplied by an electric' current varying in accordance with the ammay be employed, as for example a microphone l3 connected with any suitable type of current controlling device indicated generically as ISO Since the method of controlling the variations of the light source l2 in accordance withth'e. sound waves is well known and forms no part of the present invention, it is neither described nor claimed. I

The-light I emitted bysource II, we pass through an appropriate color filter M, the slot 3 in the aperture plate 4 and on to the film 5. Since the optical system, and the method of feeding the film'form' no part of the present invention and since any of several well known optical systems and film feeding methods may be employed, we do not describe or claim them.

. .The exact filter to be used will depend upon the photographic characteristics of the emulsion It is in effect 5 lit selected. It win be readily understood that with the the use of any monochromatic light all of area of the film which is exposed or illuminated at the same instant will be of practically uniform density. For example, if we elect to employ light of approximately 4000 Angstrom units, we will use a filter ll adapted to prevent the passage of all light other than such as will register between 9 and 9, inclusive, as shown in Figures 1 and 2. The image so created upon the film will have sharp demarcation along the lines separating band 9 from band 0 and band 9' from band I. That is, each illuminated or exposed area will be clearly and sharply defined and its so called photographic contrast great. Irrespective of the type of -monochromatic light employed, the sharpness of difierentiation or contrast will be increased over such as obtained with polych'romatic light and the raggedness caused by the use of such light largely eliminated. It should be noted, however, that the relative excellence of the result will depend upon the selection of the wave length particularly appropriate to the overcome difiiculties caused by the so called grain of the emulsion, relatively slow emulsion, such as, for example, those of 120 according to the rating of Hurter and Driflield, have been recommended for'sound films. By' the use of photographically' active wave lengths, such as for example those in the vicinity of 4000 Angstrom units, we secure with such a slow emulsion in a relatively short period of exposure the same results as others secure in a much longer and hence impractical period of exposure.-

It will be understood that instead of using rays" 7 of one wave length only, we may employ rays of .a

group of related wave lengths.

In carrying out our invention we may simultaneously record the images representing sound upon .the same film as that upon which the images representing action are recorded. Or we may make records of each series of images upon diii'erent films and subsequently impose the im-,

C L through whichlight I from the action or scene being recorded is focussed through the aperture 3 upon the film 5. It will, of course, be understood that a certain portion of the film is reserved for the action images and another sep- 60 arate portion tor the sound images, the respective \apertures 3' and 3 being so designed as to direct the light beams I and I upon the appropriate portions of the film.

In those cases in which the sound and pictorial records are placed upon the same film, we may prefer to use an emulsion rated between 120 and 200 according to the scale of Hurter and Drifii'eld. An emulsion of. a speed of 180 upon that rating may be taken for purposes of illustration.

For an emulsion of such a speed. with the latent image oi the sound record produced by monochromatic light, as for example that of approximately 4000 Angstrom units, and'the pictorial portion produced by polychromatic light, we prefer to use glycin; known as gamma oxyphenyl photographic emulsion selected. In recent practice, in order to -or gamma oxyphenyl-amido-acetic acid, as the developing agency. Under such conditions, glycin will produce the necessary contrast in the sound image and at the same time build up the half tones of the action image. It will be readily understood by those skilled in the art that for pleasing results in reproduction the sound images require great contrast and the action images full gradation. If, however, polychromatic light is used for the sound images, the glycin development would tend to reduce the contrast in the sound images to a point which will result in unsatisfactory reproduction. If a hydrochinone developer is used, the sound image made with light of a wave length of 4000 Angstrom units would be satisfactory but the pictorial image, which is of course always recorded by polychromatic' light, would be unpleasantly harsh. If a hydrochinone developeris used with a sound image made by polychromatic light, a period of development is necessary in order to secure proper contrast in. v

the sound image which will still further increase the unpleasant harshness of the pictorial image.

The use of glycin is desirable also because it tends to reduce the grain. As is well known in the art, a slow emulsion has less grain than a more rapid one.- Hence we prefer to use as slow an emulsion as is consistent with the demands of the pictorial image. Only with the use of monochromatic light is it possible to secure, in a way practical in sound recordaticn and reproduction, the use of both of these factors, namely a relatively slow emulsion and glycin development, which tend to eliminate the difficulty caused by grain.

,In glycin development, the following stock solution may be prepared:

Water. 1120 32 ounces Sodium sulphite, NazSOa, anhydrous- 360 grains .Glycin, CHiOHNHCH=-COOH 120 grains Sodium carbonate, NazCOa, anhydrous 360 grains The chemicals should be dissolved in the above order. Fahrenheit temperature between 100 and 120 degrees. p 7

For use with the emulsions of the speed stated above, such stock solution may be diluted at the ratio of one part stock solution to three parts water. The film may be developed for thirty minutes, preferably at about 65 degrees Fahrenheit. After such development. the usual steps of washing, fixing, and final washing may be taken.-

We prefer to keep the film totally immersed during the entire period of. developnwnt in order to minimize oxidation fog. We have found that the elimination of such fog is an important item in securing clear and sharp sound images.

Glycin is a developer'which produces a minimum of such fog, but toprevent the possible formation of such fog, we may prefer to use a bath of pinakryptol green, in a dilution of one part to five thousand parts of water, before the development as by the use of glycin.

In those cases in which the sound images are to be recorded alone, without pictorial images upon the same film, we may prefer an emulsion rated on the Hurter and Drifiield scale between 20 and 120.

latent pictorial image thereon, we may use any such as hydro- 75 iii The water should preferably be of a chinone, such as comonly known and used in the photo-engraving art.

'It will be understood that we do not restrict ourselves to ,the' particular formulae, methods,

,,,to; an emulsion having the color sensitivity commonly known as panchromatic together with a ,filter fQl' thB pictorial portion of the film. Such a filter maybe of a yellow color. and of the type commonly known in the photographic art as K3. the sound image, we may prefer to use a light of approximately 4000 Angstrom imits. because sucha light, in combination with a pan chromatic emulsion, produces great contrast. The polychromatic light, modified as is well knowninthe art by the K3 filter, produces an imagewhich is soft and pleasing. Glycin development of; such a film gives satisfactory results in bothportions. In this case, however, with the use of panchromatic film, we may prefer to use a preliminary bath of pinakryptol green diluted at a raftio of one part to four thousand parts of water. I I

For the-purposeof still further illustration, it may-be assumed that it is desired to produce a -.combined and pictorial film under condito be recorded, for example, .may be rapid or lightconditions poor and not subject to control as in a studio. An emulsion of a speed -on the Hurter and Drifiield scale of over 450 may be chosen. Under such conditions/a. monochromatic light-of 4000 Angstrom units may be too rapid .in its. action. In such cases, we prefer to use for thesound recordation a filter which will transmit light of a suitable wave length or group of wavelengths as, for example, any wave or group of wave lengths between 4500 to 5800 Angstrom units, depending upon the particular .of special emulsions which, after the images im-' planted thereupon have been developed and rendered visible, have peculiar characteristics of permeability by or absorption vof light waves of particular-wave lengths in combination with the photoelectriccell of particular characteristics in assoundreproducing instrument. It will be understood that we use regular stock photographicfilmsknown as black and white, which can be readilyv and cheaply obtained throughout theworld'choosing such films, however, in accordance with the purely photographic characteristics thereofiawhich are useful for the particular'purpcseiset .forthin this specification. Our choicepof. an-emulsion of a particular speed is fconditioned the photographic characteristics of -the.latent'-images which can be implanted thereonfibyijthe 'use' of light of a particular wave 'length, and the photographic characteristics of the .vislblemndxstable images which can be developedxfrnmfis'uchlatent images. Although our inventionhan be: applied tothose types of apparatus in which separate films are employed for ani and the sound and pictorial records, it is also equally applicable to those types of apparatus in which one film is used to carry both such records. It

will be readily understood thatsuch a single film bearing both such records must be chosen, exposed, developed, duplicated and projected in accordance with all the requirements of both such records. As is made clear throughout this specification, our method is soadapted to create a single film which bears both typesof records thereupon.

. Figure 4 represents diagrammatically the application of our invention to a sound recording device which depends-upon a movable mirror of the so called "galvanometer, Pallophotophone,

or Hoxie type. A light source l5 of fixed intensity is provided, the light from which passes through a color screen ll and impinges upon a niovable mirror IS the light rays from which pass through the slot 3 in the aperture plate I and impinge upon the'film 5, in this case creating images which take the form of a. wave line and create an oscillograph. The movement of the mirror I 6 is actuated through the control device l3 and the microphone 18, which, being well known in the art, are indicated merely for purposes of illustration, it being understood that they form no part of the present invention.

In recording devices as heretofore known, which have used polychromatfc light, the slot often has been constructed as narrow as possible and placed in contact with the moving film or I separated from it by a thin cover or glass in tions which require a fast emulsion. The action structed, to keep them free from particles of dust, dirt, emulsion, and celluloid brought to them and deposited by the moving film. When cover glasses for the slot havefbeen used. with polychromatic light, difiiculties caused by the varying degrees of refraction of the component parts of white light havebeen added to those .caus'ed, as stated above, by the different degrees of diffraction.

It will be readily seen that by the use of our invention it is possible to employ a slot some.- what larger in size than has been common and free from contact with the film, since although.

the actual area of the-exposure, or of exposed area to be projected for reproduction, may be somewhatlarger than in the past, all of this area is effective for the true recordation or reproductlon of the image which represents the sound, none of the same being obscured in the twilight zone of fringing colors and impairing the quality 'of tone reproductions. Moreover, by the use of rays of the shorter wave lengths, such as shown as falling between .8 and 8', 9 and 9', and i0 and M, in Figures land 2, it is entirely possible to eliminate sufiicient width of the area of exposure to compensate in part for the small fraction of nch which the slot is removed fromthe film its slightly larger width, and that without the employment .of other means hereafterydescribed. Generally speaking,- however, owing to the edge difiraction of rays of any length, the

recorded image, fromfthe larger slot s'o'spaced;

with the one of parallel or divergent light, will be slightly greater than the area of the slot,

It will be understood, also, that under our invention cover glasses can be employed without the disadvantages arising from the difierent.re-. ts an image of the slot which isin no m iiiiractive characteristics of the component of polychromaflc li ht of our 5 in a form much exaggerated. 3i-is a parts glasscover tor the slot 3 cemented to the aper-- ture plate 0. With'the use oi polychromatic light, only those portions of the film Lying be- II and il will receive or project an image without muddiness due to color aberration.

caused by difiraction and complicated by re- I u v By reason or the impinging of light of varying photographic eifectiveness due to varying colors.

along the edges of the normally; exposed line or mass upon the film. various aberrations occur in the resulting record film; These aberrations re,-

sult in an incorrect reproduction of theoriginally recorded soimd. As is well known, glass or other similar surface 3| will refract all rays which strike it save those which are at right angles rays will resume a course parallel to their nor- -mal course. In figure 5,- the dotted lines show represents the area free from color aberrations;-

Ultra violet'rays do not pass the glass, but if quartz were used, for example. the. refraction would be similar in kind although diiferent in degree to the refraction oi visible rays as described above.

With the use of monochromatic llght, however,

7 say of 4000 Angstrom units, for purposes oi illustration, the image will be'restrlcted to.the area lying between 9 and 3' and all of it will be true because of uniform density. Thus the film in position 5 in Figure 5 with monochromatic light will receive an image. all of which is eifective. and true, which is not greatly ii any enlarged over that of the image of the film in polychromatic light in position 0'; much 01' such latter image being ineffective and untrue.

Otherpreierred embodiments of our invention. however, make it possible to use a relatively large slot. .run the film out-oi contact with it, and photograph an image which is relatively very much smaller than the area of the slot. -,we accomplish this result either with or;with'out the introduction of optical elements, and with the I use of light oi a selected wave length or group type generally known'in the optical. a'rtas. apoof wave lengt According to one of these embodiments of our invention, as is clearly shown in Figure 6 of the drawings, we introduce a suitable optical element 32, such as for example a positive lens of the chromatic, between the slot 3 and the light sensitive surface I. We project light from the source l3, varied as previously set forth by the involved-through the slot 3 in the aperture plate. Tl andthrough the lens 23 or other suitable optical element. upon the light sensitive surface 5.

Thus by the use ofmenochromatic light weproinvention is 4 indicated in Upon emergence, these. refracted.

fected by the aberrations common to white light and which is therefore reproduced upon the photosensitive surface 3 without loss of integrity.

As is well known in the optical art, the size of the image projected upon the light sensitive surface caneasily .be controlled by the selection of a lens r the focus suited to the mechanical requirernents and by focussing the image with this lens, according to the well known law of con- Jugate foci. Thus, by' use of monochromatic light, it is possible to create upon.the photo,

sensitive material a satisfactory slot image ap- 'preciably smaller than the slot from which it is a at the surface of the film as .the' area of the image is decreased and the rapidity of the photographic action of the beam of light will be increased accordingly. It is likewise apparent that the recordation oi the images so. produced upon.

the film 3 through the optical element 22 may be made to in typelimited only by the capacityof the employed to receive and record light eifects upon minute areas voi' 8l' t sensitive substances. 1 a i It is apparent that the ability so to record "tonal variations in very great detail and almost micro- .scopic size will render possible a'vastly' increased range of tonal recordation and likewise a notable improvement in the detail of recorded sound.

' It is also apparent that the increased intensity of light available for delivery at the surface ofthe film 5 through the means described will render possible the use of whatever less photographicallyyactive rays of light and photographically slower emulsions which may be deemed desirable because of the so called .grain= or other photographic difilculties, all of which above advantages, methods and means are such as will be fully known to and understood by those skilled in the art without further description or e'xplahation in detail.

The slot 3may be constructed under our in-, vention sumciently large so that accuracy of manufacture is possible without undue cost and so that it can be' kept clean.

"According to one embodiment; as" is clearly shown in Figures land- 8, cl our invention, the i upwardly througha tunnel 29 by a fan 30 fixed in the housing 3i, the entrance thereto being suitably protected by dust-retarding material 32. A bailie plate 33 is so placed as to deflect the 'air' c1n-rent downwardly, as shown by the arrows in Figure 7. through'the slot 3. Power to operate the ianmay be. applied from the motive power of the film feeding apparatus, not shown, through the shaft 3ll-and't he gear 35, which may engage a suitable gear ot-such apparatus.

"of air, indicated in Figure 'l, by the arrows, forced Another, embodiment of our invention it possible to secure many of the results above'set Thus, as set forth above and illustrated in Figure 9, in a recording apparatus, we'may provide a variable light l2, actuated by the conable design. A mirror, not shown, may be provided if desired, as is well known in the art. The

converging light I passes through the opening 3 I in the plate 4 and, at or about its focal point, impinges upon the filmi. .The slot 3 maybe made somewhat smaller than the cone or wedge of light which it is desired to use for exposing the film 5 so that stray-rays, illustrated in Figure 9 as I", may be arrested.

As is illustrated .more in detail in Figure 10, one preferred .form of gate for films carrying sound records may consist of two transparent plates with no physical aperture whatsoever. the gate shown in section 43, the portion 45 along which the image bearing portion of the emulsion-bearing side of the film travels, is slightly relieved, as is common in the motion picture art, the edges of the film bearing upon the raised portions 45 and the section 42 which bears against the film opposite to section 43 is completely fiat and is held in position by springs 44 as is well understood in the art. When we make use of a monochromatic visible ray, the portion 41 of the plate 43 which is opposite the sound image carrying portion ofythe film is left transparent, but the re inder, left without cross markings in Figure 14, w ich is opposite the pictorial portion of the mm and its edges, is silvered. 1

If for use with an optical system such as shown in Figures 6'or 9, such transparent portion may be of relatively long length, as shown, but, if a slot image is not focussed, such portion may be reduced in size to the dimensions of a so-called optical slot". If desired, such transparent portion 41 may be so formed that it permits the passage of rays of the predetermined length only, and the filter l4 omitted. Since it is inherently strong, is available in thin sheets, and for still further reasons which will be later apparent, the plates 42 and 43 may well be made of plane quartz although we have found glass practicable. It will be readily understood that since there is no aperture or slot across which the film travels, the problem of dust and dirt is necessary to use a film gate of any kind for the I exposure of the portion of the film bearing the sound symbols.

As is shown in'Figure- 11, the film 5 is fed continuously and positively. as with positive engagment between its perforations and continuously rotating sprocket wheels 48 and their idlers 49. The sprockets 48 and their idlers 49 hold the film reasonably flat. Unless the film is very old and shrunken so that it tends to curl ,at the edges, this mechanism holds it sufliciently fiat at the point at which the light, strikes it so that a minimum of sound distortion is caused by a dis-' .tortion of the light waves caused by the film being out of plane. Much of the difficulty which under present practice is attributed to this lack of proper plane evidently is due to the variations in refrangibility of the several wave lengths composing white or polychromatic light.

According to one preferred embodiment of our invention, we employ ultraviolet light for any and all of the purposes above set forth in connection light under norm l atmospheric conditions, such.

as, for example, the electric arc and the so called Nernst lamp. accordancewith this exempliflcation, we use a light source II of some such type as we mention above in such structures as those diagrammatically represented in Figures 3, 4, 6, and 9, and in the manner described in connection therewith. In every instance in which a lens or other similar optical element is employed .in connection with ultra iolet light it must of course be constructed of quartz, as is well known in the optical art.

In order to combine aperture plate and filter, with the use of ultraviolet light, we may employ the aperture plate which is illustrated in Figures 12, 13, and 14. Two pieces of very thin glass or metal 56, separated sufficiently to form a slot 51 of the requisite width, are placed between two pieces 58 of plane quartz. It is often found easier to;cement two such pieces of glass or metal in the proper. position than accurately to cut a slot of this extreme narrowness in either glass or metal or to draw it upon a silvered surface; All of one surface or more of the quartz as required issilvered in order to stop all visible rays. 'As is illustrated in Figure 14 of the drawings, it is possible to limit the ends of the slot as desired by filling them with some material, such as asphaltum 59, which is opaque to the particular ray which is being employed. The accuracy of the ends of the .slot in most types of apparatus is not as important as is that of the sides.

In carrying out our invention in,

To secure improved and stable translation of sound images into light images,the theoretically constant light source may be maintained at a pointwhich is actually constant,;or approximately constant, as is illustrated, for example. in Figure 15 of the drawings. Obviously the difficulties causedby the change in color of the light caused by the fluctuations of the'light source is removed by the use of monochromatic light. A further embodiment of ourinvention prevents material change in light intensity, such changes causing analogous difficulties.

A common cause of change in intensity of the theoretically constant light source is found in temperaturechanges which decrease or increase the degree of incandescence of the light element. The common expedient of warming the light j source by turning on the current in advance of its use does notmcet the difficulties caused by later changes in temperature caused by conditions which later developed. We have found that the opening of a door or window in aroom in which apparatus is being used will change the visible characteristics of the light. The means shown for example in Figure 15 definitely controls the a heat of the theoretically constrnt light source.

A light source shielded and controlled as is here set forth may be used as desired in any or all of' the previously described exempliiications of our invention. The arrangement herebelow described a chamber with double walls such as "and L.

'rection' shown by the arrows.

65 may be driven in any desired way, not shown. Through the opening 66 past the bafis of particular usefulness under any conditions under which an approximately constant light source is desired. Broad claims to this phase of our invention will be found in our parent application.

In one embodiment of our invention, we may place the light source II, which for example may be an incandescent globe of any desired type, in

and preferably with an air space 8? between them. Fresh air is forced into this chamber 02 by a fan 63 rotative upon a shaft 6! to which is attached a pulley 65, and such air takes the difle plate 61 the fresh air is directed into the inner lamp chamber. The wall 6. being preferably of a heat conductive material, the fresh air, while considerably cooler than the body of air in the chamber, is not of a ternperature sufllciently low to cause a drop in the incandescence of the lamp. The heated air leaves thechamber through the vent G8 in the top, which is protected by baille plates, not shown, as is well known in the projection art, to prevent the escape element may be a plate of plane glass or quartz,

merely to complete the enclosure of the chamber, or it inay be a suitable condensing lens or fllter. A mirror or other reflecting surface ll may be provided.

In order positively to maintain the lamp II at a given-point of incandescence by holding the temperature of the chamber at a predetermined point, a thermostatic element Il may be provided which, through an appropriate electrical means, controls the amount of current which is permitted to flow into the heating units 12 which may be placed within the chamber. a

The thermostatic control of the circuits of the heating units 12 may be accomplished in any of various well known ways.- For example, the thermostatic element Il may be incircuit with the magnetic element ll which determines the movement of the wiper arm 14 so that it places more or less of the resistance 15 in circuit with the heating elements 12, thus determining their activity.

It will be understood thatwe do not limit ourselves to this type of control unit and refer to it merely for purposes of illustration.

' In order to compensate for changes in incandescence of the light source which might be brought about by changes in the temperature of the lamp chamber, or lamp house as it is generally termed in the motion picture art, we may regulate the amount of current reaching the lamp in" accordance with the temperature of the immediate vicinity of the lamp. Such means may be employed independently of theheat maintaining meansjust described, or in conjunction therewith. For simplicity, we illustrate this phase of our'invention in Figure 15, which also illustrate such heat maintaining means.

A thermostatic element 16' may be provided The pulley later set out in further detail, such control is ex- "ercised within restricted limits. The thermostatic control of the circuit supplying the source i2 may beaccomplished in any of various .well known ways. For example, the thermostatic element I6 may be in circuit with the magnetic element 'll which determines the movement of the wiper arm 10 so that it places more or less of the resistance 19 in circuit with the light source II. The range within which the current reaching the lamp is permitted so to fluctuate is very small. When a light source, particularly an incandescent light source, is operated reasonably near its point of optical efliciency, a relatively small fluctuation in the current reachin'g such source will have relatively great eifect in the intensity of its light output. It willbe understood that since uniformity and not intensity is desired, it is preferable to burn the lamp at a point well below that at which injury to the filament is likely. We prefer that the maximum current permitted to reach the lamp by the resistance 19 be suil'iciently restricted so that even when the filament is cold such maximum current will not be dangerous to the life of the filament.

-As an additional safeguard, to prevent overloading of thecircuit supplying the light source,

we may place in such circuit an automatic circuit 1 breaker an, or other similar device, or the light source I! may be fed direct from a battery or the line. This control element will positively prevent any amount of current, over the predetermined reaching the light source II.

In those cases in which the'heating elements.

and the means for the control of the circuit of the light source are jointly used, it will be readily understood that the usefulness of the latter means generally will be greater in the early stages of any period of operation. After the temperature of the lamp chamber has been brought to the desired point, it will generally be so maintained by the heating elements alone.

It will be readily understood by those skilled in I the art that the joint operation of these two means .involves no conflict. From the time of beginning operation until the temperature of the lamp chamber reaches the predetermined point,

the thermostatic element" will operate gradually to increase the amount of resistance 15 in circuit with the heating elements 12 and so render them less and less active. From that point onwardly, the fluctuations of current in the circuit feeding the heating elements 12 will be such as are necessary to maintain that predetermined point of temperature. It is understood that the ventilating device such as heretofore described when the heating units 12 are entirely inactive will prevent the temperature of the chamber from reaching a point higher than the predetermined point.

When operations begin, all resistance 19 will be out of the circuit feeding the light II, it ifdesired i being protected against overloading as by the element ll. As the temperature of the chamber increases, the amountof such resistance 19 in circuit with the light source I! gradually increases until the entire amount is in circuit when the ll in circuit. Should such temperature fall, the

which current fluctuations occur,

amount of resistance 1| would be decreased until the light source I! receives-the entire amount of current delivered from the line as through the It will thus be apparent that the method and construction abovedescribed provide extremely simple means whereby sound waves may be accurately and 'efl'ectively translated into photographic images.

Other advantages have" been referred to d throughout the specification from which it .be-

comes apparent that diil'erentembodiments of the invention may be made within the scope of the inventive disclosure hereof.

We claim:

1. The method of recording sound which con-- sists in the exposure oi photo-sensitive material to light of approximately 4000 Angstrom units Va y gv the light for implanting latent images thereon in accordance with the variation oi the sound which is beingrecorded, and developing said latent images into black and white visible homes.

2. 'The method of recording sound which comprises the exposure ot a light-sensitive material of.

a speed between 120 and 200 according to the rating-oi Hurter andDriilleld to light of a. wave length of approximately 4000 Angstrom units, which light varies in accordance with the sound which is being recorded.

3. The method of recording sound which comprises projecting light which varies in accord-' ance with the sound which is being recorded which light is of a predetermined wave length prises projecting light which varies in accordance with the sound which is being recorded which 'light is 01' a wave length of approximately 4000 Angstrom units upon a photo-sensitive material of a speed between 120 and 200 according to the rating oi Hurter andDriilleld whereby latent images are implanted thereon and developing said images with a developer which includes glycin.

5. The method of recording sound which comprises projecting light which varies in accordance, with the sound which is being recorded, which light is or a predetermined wave length, upon photo-sensitive material of a speed of between 120 to 200 according to the Hurter and Driflield rating whereby latent images are implanted thereon, reducing oxidation fog in said material, and rendering said latent images visible and stable by developing said material according to a formula which includes glycin.

6. The method or recording sound which comprises passing light thr u h a slit and upon light sensitive material, varying light from said source inaccorda'nce with the sound to be recorded, and limiting such light to rays which vibrate at substantiaily the same rate thereby minimizing the elects of chromatic dispersion caused by said 811 to ultra violet.

film, and means eiiective to maintain the incanta b v 7. The method ot-recording sound which comrlises the exposure oi light-sensitive material to 8. The method 01' recording sound which comprises positioning a source of light within a chamber, varying said light in accordance with thc-- sound which is being recorded, directinglight from said sourceupon a light sensitive film, and- 5 supplementing the heat emitted by said lightsource for maintaining .the temperature within' said chamber at a predetermined level so that the color'characteristics of light emitted by said source will'remain substantially constant.

9. The method of recording sound which con-( sists in passing a beam of light falling within a predetermined range of wave lengths upon light sensitive material, varying said light in accordance with the sound which is to be recorded, and maintaining thesource of said light at such predetermined level throughout the sound recording operation.

[10. The method of recording sound which consists in projecting light from a source the wave length of which is maintained at approximately 4000 Angstrom units upon a light sensitive film and varying said light in accordance withthe sound to be recorded while maintaining said light at approximately 4000 Angstrom units.

11. The method of recording sound which consists in continuously operating a light source positioned within a chamber, varying said light source in accordance with the sound beingrecorded, .causing said light as so' varied to fall 30 upon a light sensitive film, thermostatically regulating theamount 01' current reaching said light source in accordance with-the temperature oi said light sourceat a predetermined level whereby the color emanation of said light remains unchanged sothat the efiective light output thereof is not subject to unwanted variations.-

13. In apparatus for the recordation of sound, an electrical source of light, means for varying light from said source in accordance with the sound which is to be recorded, means for directing light from said source as so varied upon a light sensitive filni, operable means for varying the amountof current reaching said light source, and means responsive to the heat generated by said light source, for operating said current varying means.

14. In apparatus for the recordation of sound, 60 an electrical source of light continuously oper-- able, means forvarying said light in accordance with the sound which is to be recorded, means for projecting said light upon a light sensitive descence of said light source during its continued operation at a predetermined level 01 such character that the light emitted has a wave length 0'! from 2800 to 4800 Angstrom units.

15. In apparatus for the recordation 01' sound, a light source, means for varying light from said source in accordance with the sound which is to be recorded means for limiting the light to rays which vibrate at substantially the same rate,

a slit, and means for tocussing the image of said 7 slit as formed by light i'rom said source asmodifiedby'said filter upon a light sensitive film.

18. In apparatus for the recordation of sound,

a light source, means for varying light from said source in accordance with the sound which is to be recorded, means for limiting the light to rays which, vibrate at substantially the same rate, a

slit. and means for conversing light from said source through said slit and upon a light sensi-.

tive film. I 17.. The method or recording sound which com- Drises modulating a light beam in accordanceoi ultra-violet light, means for varying light mm said sourcein accordance with the sound to be means for passing a light sensitive film through light fromsaid source, and means limiting the light which reaches the film to ultraviolet.

19. In apparatus for recording sound, a source of light of approximately 4000 Angstrom units, means for varying said light in accordance with the sound to be recorded, and means for passing such light upon a light sensitive film.

20. The method of recording sound which comprises passing light through a slit and upon light sensitive material, varying the light in accord-.

ance with the sound which is being recorded. and

limiting such light to ultraviolet.

21-. The method 0! recording sound which comprisespassing light of approximately 4000 Angstrom units through a slit and upon sht sensitivematerial and varying such light in accord- 1 ance with the sound which is being recorded.

CARL oms OSWALD. WARREN mmmm r'os'rna. 

